This invention pertains generally to well workover systems and more specifically to casing packoff systems used during a well workover process.
Most oil wells are constructed of an outer casing through which production tubulars are passed. The casing maintains the integrity of the well by preventing the formation material through which the well passes from entering the well bore of the well. Over time, the casing may develop perforations because of the effects of corrosion or mechanical damage caused by tripping tubulars and downhole tools through the casing. These openings may allow undesirable formation fluids to enter the well bore. More importantly, these perforations may allow desirable fluids, such as production fluids from lower formations or drilling fluids, to leak from the casing into a formation, thus causing a loss of these desirable fluids.
Once a casing has developed such leaks, an operator has very few options to remediate the well. One option includes injecting cement into the perforations, termed a “squeeze job”, in hopes that the cement will fill the perforations and stop the casing from leaking. Sometimes during a squeeze job the cement migrates to producing zones and the well must be re-perforated in the desired producing zones before it can be used again. Another option is to re-case the well using a smaller diameter casing. As these options are expensive, the well may simply be abandoned if it is a marginal producer. Therefore, a need exists for an inexpensive packoff system for well casing.
Another instance where a packoff system for a casing may be desirable is when an operator wishes to take an existing producing well and enhance its production by drilling into deeper zones or by drilling additional lateral well bores radiating from the well. During the drilling process, the operator may need to temporarily seal off a currently producing zone in the well. In this case, both squeeze jobs and re-casing of the producing zone are too permanent as these solutions will require additional reworking of the well in the currently producing zone to bring the well back into production. Therefore a need exists for a removable casing packer or a casing packer that is so inexpensive that it can be sacrificed during removal.